A retrospective case-control study evaluated the ability of DWI to detect hemorrhagic stroke in 86 patients who presented with symptoms consistent with acute stroke.3 Investigators compared the sensitivity and specificity of DWI against the pooled results of 5 different MRI sequences. Both case and control imaging was performed within 6 hours of symptom onset. Half of the patients in the study had hemorrhagic strokes (43); the rest had ischemic strokes (41) or a TIA and postictal deficit (2). The sensitivity and specificity of DWI for hemorrhagic stroke were both 1.0. However, there was no independent reference standard.
MRI costs more than CT
Although costs vary widely, one textbook put the national average charge for a head CT at about $1000.4 MRI neuroimaging charges ranged from $1000 to $4700, with an average of about $2300. Medicare reimbursements were significantly less, although the cost of MRIs was still about double that of CTs.
Recommendations
The Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology says that DWI is more useful than noncontrast CT for diagnosing acute ischemic stroke in patients presenting within 12 hours of symptom onset.5 The subcommittee made no recommendation for imaging hemorrhagic stroke.
American Heart Association and American Stroke Association guidelines for early management of adults with ischemic stroke recommend neuroimaging with either DWI or CT within 45 minutes of arrival in candidates for tissue plasminogen activator.6 They also recommend neuroimaging with either CT or MRI to distinguish ischemic from hemorrhagic stroke.7 The guidelines state that other imaging methods (including CT angiography, contrast-enhanced MRI, and magnetic resonance angiography) “may be considered” to evaluate for clinically suspected underlying structural lesions, including vascular malformations and tumors.